Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 301
Narrated Abdullah bin Umar:
The Prophet said, "The keys of the Unseen are five." And then he recited:
'Verily, the knowledge of the Hour is with Allah (alone).' (31.34)